The Science Inside Skin
Total Page:16
File Type:pdf, Size:1020Kb
the science inside SKIN AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE Dear Reader: Science data and statistics are always changing, and it is important to be informed of current research. To help keep you up-to-date with the latest information on skin health, the American Association for the Advancement of Science would like to share the following updates regarding skin health: N Major medical groups, including the CDC, recommend using sun- screen with an SPF of 15 or higher. However, a growing number of health care providers, including the M.D. Anderson Cancer Center, suggest products of SPF 30 or higher, particularly for those whose skin burns easily. (See references on pages 17, 32, and 45.) N The number of doctor visits Americans make each year to get skin rashes checked out has dropped from 11.8 million to 10 million, according to the National Ambulatory Medical Care Survey: 2006 Summary, National Health Statistics Report No. 3. (See reference on page 23.) http://www.cdc.gov/nchs/data/nhsr/nhsr003.pdf is the most recent data. Check the site for regular updates to the statistics. N According to the CDC’s National Program of Cancer Registries, 53,792 new cases of melanoma were reported in 2005, the most recent year for which statistics were available in Summer 2009. The National Cancer Institute estimates that 68,720 new cases will be diagnosed in 2009. (See reference on page 36.) N Estimates vary as to the likelihood of developing melanoma during the average American’s lifetime. MedlinePlus, developed by the National Institutes of Health, estimates that 1 in 65 people will be diagnosed with melanoma at some point in their life. In 2009, The Skin Cancer Foundation predicted that 1 in 55 people will be diagnosed. (See reference on page 36.) As the science advances it is possible that more recent data will provide you with different numbers. While you can use this book as a starting point, check credible sites, such as those above, for results on the most up-to-date research. the science inside SKIN AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE Published 2009 by The American Association for the Advancement of Science (AAAS) 1200 New York Avenue, NW Washington, DC 20005 © Copyright 2009 by AAAS 978-0-87168-713-5 All rights reserved. Permission to reproduce this document for not-for-profit educa- tional purposes or for use in a review is hereby granted. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photocopy, recording, or otherwise, for commercial purposes without prior permission of AAAS. This publication was made possible by a grant from Neutrogena. Any interpretations and conclusions contained in this booklet are those of the authors and do not represent the views of the AAAS Board of Directors, the Council of AAAS, or its membership, or of Neutrogena. TABLEOFCONTENTS INTRODUCTION: HEALTHY SKIN ................................1 PART 1: SKIN FORM AND FUNCTION.............................3 What is skin? . 3 Why do we have skin? . 7 PART 2: HEALTHY SKIN.......................................13 A lifetime of skin. 13 Babies’ skin . 13 Teenagers’ skin . 15 Adults’ skin . 16 Healthy Hair and Nails . 19 Hair..................................................19 Nails . 20 PART 3: SKIN DISORDERS AND TREATMENT......................23 Skin Allergies. 23 Eczema . 24 Contact dermatitis. 24 Hives. 25 Psoriasis . 27 Acne....................................................28 PART 4: SUN EXPOSURE AND SKIN CANCER .....................31 Sun and your skin . 31 What is skin cancer? . 32 PART 5: PROMISING RESEARCH: THE SKIN CARE OF TOMORROW. 39 The basics of skin growth. 39 The genetics of skin diseases . 39 Psoriasis . 40 Skin cancer. 41 Acne....................................................43 The important role of volunteers . 44 CONCLUSION: WHAT YOU CAN DO TO HAVE HEALTHIER SKIN . 45 APPENDIX 1: QUESTIONS TO ASK YOUR DOCTOR ABOUT YOUR SKIN .......................................47 APPENDIX 2: TAKING PART IN RESEARCH STUDIES— QUESTIONS TO ASK ......................................48 APPENDIX 3: OTHER SKIN CONDITIONS .........................51 RESOURCES ................................................55 BIBLIOGRAPHY .............................................61 GLOSSARY ...................................................... 65 ACKNOWLEDGEMENTS........................................... 69 PHOTO CREDITS ................................................. 70 INTRODUCTION: HEALTHY SKIN kin is the body’s largest organ. It is also the most visible. A square inch of skinS has millions of cells and many nerve endings for sensing temperature, pain, pressure, and touch. It keeps us shel- tered from the elements and protects our insides from drying up. Yet despite its toughness, skin is sensitive and can be damaged if it isn’t cared for. It requires our protection from the sun and from irritants. It needs our help in retaining moisture. It demands a little thought now and then. In this book, you will learn all about your skin and how to take care of it. You will learn about skin ailments, from acne to skin cancer, and how to prevent them. The body sheds 30,000–40,000 dead Finally, we will look at the skin cells off its surface every minute. promising research scientists are doing to improve skin This amounts to nine pounds of care to keep your skin cells every year. healthy for a lifetime. 1 Skin: The Science Inside Your skin is about 1/10 of an inch deep. The thinnest skin on your body is on your eyelids and on the inside of your elbows, and the thickest skin is on your palms, the soles of your feet, and your upper back. 2 Part 1: Skin Form and Function HAIR EPIDERMIS PORE NERVES DERMIS FATTY OR SUBCUTANEOUS TISSUE HAIR FOLLICLE OIL GLAND BLOOD VESSELS SWEAT GLAND A cross section What is skin? dermis mostly builds new skin of the Skin is actually made up of three cells and makes melanin, a three pigment that gives skin its layers different layers: of skin color. When we go outside, the • The epidermis melanin in our skin helps protect • The dermis us from being burned by the • The subcutaneous tissue sun’s ultraviolet rays. The epidermis is the top layer Basal cells form the bottom of of skin, the part you see. Only as the epidermis. They divide and thick as a sheet of paper, the epi- form squamous cells, which 3 Skin: The Science Inside produce keratin, a protein that of your immune system, are also reinforces your skin cells to help found in the basal layer of your protect you from the environment. epidermis. As the basal cells divide, they push The dermis is the middle layer of the squamous cells up toward the our skin and makes up the majori- surface of your skin. As they move ty of it. It includes strong fibers up, the cells shrink, flatten, and called collagen and elastin, die. When they reach the top layer which give our skin strength and of the epidermis, they become the elasticity. stratum corneum, the outermost layer of skin that protects the The dermis contains sweat body. glands, oil glands, blood vessels, nerve fibers, lymphatic channels Melanocytes, which make the (the tubes that carry the bodily melanin in your skin, and fluid lymph), hair follicles, and Langerhans cells, which are part muscle cells. A cross section of dermal and epidermal skin layers 4 Part 1: Skin Form and Function Why are there different skin/hair colors? No one can deny the importance of skin main determining factor in what color a color within our society. Socially it can person’s skin will be, there is also another affect many things, but scientifically, skin pigment located in the dermis, which color is a lot less complex. contributes to the color. This yellow-col- ored pigment, called carotene, is covert- Most scientists agree that sunlight levels ed to vitamin A. Along with the pigments, determine whether a population tends to there are other factors that contribute to have light skin or dark skin. Sunlight con- skin color, such as the subcutaneous, or tains ultraviolet radiation (UV). The dark- fatty, tissue layer of skin. The way that er the skin, the less UV penetrates into it. light filters through this layer, as well as Too much UV is bad, because it destroys the other two layers of skin, has an effect an important nutrient, called folate. But on the way that skin color is perceived. some UV on our skin is good, because it Sometimes skin color develops unusually. helps our cells produce vitamin D, another Most people have moles (also known as important nutrient. birthmarks or nevi). Generally these are Where there is a lot of direct sunlight, just harmless clusters of darkly pigmented like in places close to the equator, people cells, but they should be watched because get more than enough sunlight to pro- changes can warn of developing skin can- duce vitamin D, but they are very suscep- cer. Vitiligo is an autoimmune disease tible to folate damage. Having dark skin that causes the skin to develop milky- that protects against the destruction of white patches. These develop because folate is advantageous in these parts of the body mistakenly makes antibodies the world. As a result, people with genes to its own melanin. for dark skin are healthier and produce Hair color is also a result of how much more offspring, who also have darker melanin a person has in their body. skin. After many generations, populations Individual hair shafts grow from follicles in these areas are mostly dark-skinned. that are rooted in the subcutaneous layer, Where sunlight is weak, making it diffi- passing through the dermis and epider- cult to produce enough vitamin D, the mis. Each hair is geneti- genes that produce light skin are favored, cally programmed allowing more UV to penetrate. In these to produce a certain parts of the world, people with those amount of melanin.